1. Field
This patent specification relates to a method and apparatus for Internet facsimile transmission, and more particularly to a method and apparatus for Internet facsimile transmission that can effectively decrease communication costs.
2. Description of the Related Arts
Transmission of image data is widely used through equipment such as facsimile machines or data communications terminals such as PCs (personal computer) coupled through a public switched telephone network (PSTN). For such image data transmission, a user typically pays charges determined in accordance with communication time and distance. Usually, the longer the call distance, the higher the charge.
The Internet is a newcomer of the communication and brings a new charge system that usually is not based on call distance. Accordingly, a system that uses the Internet for facsimile transmission has recently been developed. More specifically, a facsimile transmission between two data communications terminals such as facsimile machines is relayed through the Internet using gateway terminals. The major portion of the call distance is thereby covered by the Internet and the PSTN is only used between the facsimile machine and the gateway. The communication costs will accordingly be decreased.
Published Japanese Unexamined Applications, No. 10-107938 and No. 11-55487, describe examples of the above system.
The conventional Internet facsimile system, however, has a drawback. For example, in a real-time-type Internet facsimile system, a user is charged even when a facsimile transmission has failed. More specifically, a line connection between a calling facsimile machine and a gateway terminal is established when the gateway terminal accepts a call sent from the calling facsimile machine, regardless of whether a called facsimile machine can accept the call or not. For example, when the called facsimile machine is busy, the gateway terminal will fail in establishing the line connection. In this case, the user will be charged for a time fee of the communication between the calling facsimile machine and the gateway.